XIII. Poirot Explains

"When I found that the more efforts I made to clear him, the more
efforts he made to get himself arrested. Then, when I discovered
that Inglethorp had nothing to do with Mrs. Raikes and that in
fact it was John Cavendish who was interested in that quarter, I
was quite sure."

"But why?"

"Simply this. If it had been Inglethorp who was carrying on an
intrigue with Mrs. Raikes, his silence was perfectly
comprehensible. But, when I discovered that it was known all
over the village that it was John who was attracted by the
farmer's pretty wife, his silence bore quite a different
interpretation. It was nonsense to pretend that he was afraid of
the scandal, as no possible scandal could attach to him. This
attitude of his gave me furiously to think, and I was slowly
forced to the conclusion that Alfred Inglethorp wanted to be
arrested. Eh bien! from that moment, I was equally determined
that he should not be arrested."

"Wait a minute. I don't see why he wished to be arrested?"

"Because, mon ami, it is the law of your country that a man once
acquitted can never be tried again for the same offence. Aha!
but it was clever--his idea! Assuredly, he is a man of method.
See here, he knew that in his position he was bound to be
suspected, so he conceived the exceedingly clever idea of
preparing a lot of manufactured evidence against himself. He
wished to be arrested. He would then produce his irreproachable
alibi--and, hey presto, he was safe for life!"

"But I still don't see how he managed to prove his alibi, and yet
go to the chemist's shop?"

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Poirot stared at me in surprise.

"Is it possible? My poor friend! You have not yet realized that
it was Miss Howard who went to the chemist's shop?"

"Miss Howard?"

"But, certainly. Who else? It was most easy for her. She is of
a good height, her voice is deep and manly; moreover, remember,
she and Inglethorp are cousins, and there is a distinct
resemblance between them, especially in their gait and bearing.
It was simplicity itself. They are a clever pair!"

"I am still a little fogged as to how exactly the bromide
business was done," I remarked.

"Bon! I will reconstruct for you as far as possible. I am
inclined to think that Miss Howard was the master mind in that
affair. You remember her once mentioning that her father was a
doctor? Possibly she dispensed his medicines for him, or she may
have taken the idea from one of the many books lying about when
Mademoiselle Cynthia was studying for her exam. Anyway, she was
familiar with the fact that the addition of a bromide to a
mixture containing strychnine would cause the precipitation of
the latter. Probably the idea came to her quite suddenly. Mrs.
Inglethorp had a box of bromide powders, which she occasionally
took at night. What could be easier than quietly to dissolve one
or more of those powders in Mrs. Inglethorp's large sized bottle
of medicine when it came from Coot's? The risk is practically
nil. The tragedy will not take place until nearly a fortnight
later. If anyone has seen either of them touching the medicine,
they will have forgotten it by that time. Miss Howard will have
engineered her quarrel, and departed from the house. The lapse
of time, and her absence, will defeat all suspicion. Yes, it was
a clever idea! If they had left it alone, it is possible the
crime might never have been brought home to them. But they were
not satisfied. They tried to be too clever--and that was their
undoing."